This invention relates to high viscosity polar oils useful for use in cosmetics and toiletries comprising complex polyol polyester polymers and blends thereof, their method of production, and their use.
Both natural and synthetic ester oils are used extensively in cosmetic and toiletry applications. In contrast to mineral oils, ester oils contain the polar ester linkage that provides substantivity to the skin and to the hair by electrostatic attraction. The ester oils provide a variety of benefits such as skin lubrication, moisturization, conditioning, and modification of the initial feel and after-feel of cosmetic formulations. Furthermore, they provide conditioning and shine enhancement to the hair. Many ester oils are available to the industry, each providing benefits that can be predicted through examination of basic physical properties such as viscosity, viscosity temperature behavior, melting point, density, hydrophilic/lipophilic balance and/or solubility parameter, refractive index, and others. Due to the fundamental structure of non-polymeric ester oils and the limitation of commercially available carboxylic acids and alcohols available for their production, the viscosity range for these oils is limited.
In certain instances, a higher viscosity which is not obtainable through simple ester chemistry is a desirable benefit. Ricinus communis seed oil (castor oil) is unique among the natural triglyceride oils because its high viscosity (approximately 6 to 8 poises at 25° C.) facilitates a delay in the settling of pigments in color cosmetic product, and acts to delay the tendency of the formulated cosmetic product to smear or run off of the skin. Castor oil primarily consists of glyceryl triesters of ricinoleic acid (an unsaturated fatty acid). It is therefore a molecule that contains three hydroxyl groups, making it significantly more polar than most triglyceride oils. This higher polarity increases its “solvent power” (the ability of a solvent to dissolve many polar formulation ingredients, particularly organic staining dyes that are used extensively in color cosmetics). Castor oil is currently used extensively in personal care products for topical application to the skin such as lipsticks, lip glosses, eyebrow pencils, eyeliners, eye shadows, mascaras, face powders, moisturizing creams, lotions, gels, and suntan/sunscreen products. It is also used in a variety of hair care applications such as conditioning shampoos, conditioners, hair waxes, hair dyes and colors, hair bleaches, hair tonics and grooming products, and hair sprays. It is also used in bath and body care formulations such as bath oils, shaving preparation products, and bath soaps and detergents.
Castor oil has disadvantages in that it tends to have a disagreeable odor and distinctive unpleasant taste, described by some as “bitter” or “sickly.” Castor oil is also poorly resistant to autoxidation due to unsaturation in the fatty alkyl portions of the molecule, and thus will tend to quickly develop further intensified odor and taste when heated, which is necessary such as in the production of many personal care products, particularly lipsticks. For example, if significant oxidation occurs during lipstick processing, the molten lipstick can tend to increase and/or change in color, to increase viscosity, and to form insoluble precipitants and films. At room temperature, degradation still occurs but at a slower rate; however, the rate can be quite variable depending upon the thermal and oxidative history of the oil prior to use. This can lead to major variation in the batch to batch stability and therefore the shelf life of the article produced.
To improve its resistance to autoxidation, castor oil can be hydrogenated to reduce its unsaturation; however, to achieve acceptable oxidation resistance, the required level of reduction in unsaturation by hydrogenation is such that its melting point increases resulting in a product that is solid at room temperature, which is not useful for many applications. In color cosmetic products, castor oil can retard the penetration of oils into lumps of dry pigment during the mixing operation, and can cause a feeling of friction or drag when the cosmetic product is applied.
Additionally, the United States is totally dependent upon imports to meet industry demands for castor oil, as the castor bean is only cultivated significantly in India, and South America.
Despite these serious technical and economic disadvantages, castor oil continues to be used extensively because of the absence of a suitable replacement in terms of performance and/or cost. Therefore, there is a need in the cosmetic industry for a product that has a similar viscosity and polarity to castor oil, has good solvent power for staining dyes, has an equivalent or higher viscosity index than castor oil, exhibits reduced drag, has less odor and color, has greater resistance to autoxidation, can be sourced dependably, while remaining cost effective.
As of yet, this need is unfulfilled. Research has been conducted into the development of alternative seed crops that can deliver a natural oil that has similar characteristics to castor oil. Increased cultivation of castor beans in the United States is infeasible since the seed, leaves, and stem of the castor plant are poisonous to humans and livestock; the ingestion of even one seed can be fatal to humans. Seeds of the castor plant contain ricin, a powerful toxin that can induce hepatic lipid peroxidation, glutathione depletion, and severe liver necrosis and is considered by the U.S. government to be an agent of biological warfare. Thus, those seeking to cultivate castor beans in the U.S. may be subject to various regulations and restrictions.
Currently, a program is in place to develop the cultivation of Lesquerella fendleri (bladder pod), since its seeds contain fatty acids that are similar to those present in castor oil. However, progress has been slow in the development of this alternative, and field and greenhouse experiments have shown that Lesquerella production under the conditions prevailing in the United States may not be feasible.
Higher viscosity synthetic esters have been developed, such as pentaerythritol tetraisostearate (CROMAMOL® PTIS, Croda Corporation, Parsippany, N.J., United States of America), PURESYN® ME100, PURESYN® ME450 (ExxonMobil Corporation, Edison, N.J., United States of America), and LEXFEEL® 350 (Inolex Chemical Company, Philadelphia, Pa., United States of America), which provide the viscosity needed for effective pigment dispersion; however, they are too low in polarity as they do not contain the hydroxyl functionality that is required to be a suitable replacement for castor oil.